NEW ORLEANS — A train conductor was seriously injured and an engineer suffered minor injuries when a freight train hit a truck Sunday in northeast Louisiana, derailing two engines and 17 cars, according to Union Pacific Railroad Co.

The conductor's injuries were not considered life-threatening, Union Pacific spokesman Jeff DeGraff said. He said the conductor was airlifted to a hospital in Shreveport — about 120 miles west of Mer Rouge, where the accident occurred Sunday afternoon — and the engineer was taken to a local hospital.

"Out of concern for the privacy of our employees, we are not releasing their names," DeGraff said in an email.

Both were in a locomotive that overturned and slammed into a big oak tree, Mer Rouge Police Chief Mitch Stephens said. He said the locomotive ended with its main door facing the ground and rescue crews had to pry off an access door to get to the two.

Stephens said about 50 houses were evacuated for about two hours due to concerns that a tank car of pressurized argon gas might explode. Another tank of argon, an inert gas used to fill light bulbs and in arc welding, leaked until it was empty, he said.

Stephens said the trailer got stuck on the tracks crossing Highway 165, but trucker Daniel Shackleford, of Freedom, Missouri, was unhurt. Shackleford was hauling a rig owned by Taylor Truck Line of Northfield, Minnesota.

"He saw the train coming and he jumped out of the truck," Stephens said.

The train was hauling 87 cars, DeGraff said.

The police chief said the transport trailer got caught on the tracks.

"It was a lowboy. We've had this occur numerous times in the past, where trailers would get hung up on tracks," he said.